Water's boiling point is 212F, yet there is still water in the kettle after boiling for over an hour.
Chlorine is highly volatile at standard temperature and pressure. In fact it prefers to be a gas. But water, not so much. Water has a high "heat of vaporization" at standard temperature and pressure, and can only evaporate up to 100% relative humidity near the kettle, beyond which it evaporates and recondenses at the same rate. It would much rather be liquid water at standard temperature and pressure, but will reluctantly convert to vapor with a lot of energy.
Yes, chlorine (which is actually a very low concentration in the form of hypochlorite which degrades to form chlorine gas) will evaporate out of water to non-detectable levels at standard temperature and pressure if left overnight prior to brewing.